1. Field of the Invention
The present invention relates to a solid-state imaging device in which photoelectric conversion efficiency per unit pixel is improved and to a method for fabricating the solid-state imaging device.
2. Description of the Related Art
In solid-state imaging devices, photoelectric conversion efficiency per unit pixel has been improved by increasing the aperture ratio in the unit pixel or by increasing the light collection efficiency of microlenses.
Recently, in solid-state imaging devices, a further increase in the number of pixels has been taking place, resulting in a decrease in the area per unit pixel, and thus a further improvement in photoelectric conversion efficiency has been desired. Therefore, for example, in the case of a photodiode, in a PN junction structure, the impurity concentrations in the individual regions are increased, and thereby the photoelectric conversion efficiency is improved (refer to Kazuya Yonemoto, “CCD/CMOS imeji sensa no kiso to oyo (Basics and Application of CCD/CMOS Image Sensors)”, CQ Publishing Co., Ltd., pp. 92-94).